Recently, download sales of software and music contents performed via a network has become widespread. In downloading contents, a purchaser connects to a contents sales server via a net work and by using a terminal apparatus such as a personal computer and a PDA (Personal Digital Assistant), and inputs required items relating to payment (e.g. credit card number of the purchaser) according to instructions given on the purchasing screen displayed in the display unit of the terminal apparatus.
After the download completion, the contents sales server transmits an electronic receipt, which has contents corresponding to a paper receipt and is used as proof of purchase in place of a paper receipt, to the terminal apparatus via the network.
An electronic receipt has many advantages over a paper receipt. For example, an electronic receipt can be transmitted easily and promptly from the server via a network and can be stored and read easily at a reception terminal.
In many current cases dealing with receipts, however, only paper receipts are accepted or trusted.
Patent reference 1 discloses a system for printing an electronic receipt on paper for use. In this system, an output control apparatus of receipt data receives from a host apparatus (i.e. server) electronic receipt data being original data according to which printing data and the electronic receipt are generated. After reception of the electronic receipt data, the output control apparatus generates the printing data and the electronic receipt according to the electronic receipt data, and outputs the printing data to a corresponding printer, and the electronic receipt to a corresponding electronic-receipt reception apparatus.
Whenever an electronic receipt becomes necessary again because of loss of the electronic receipt for example, the electronic-receipt reception apparatus is able to obtain the same electronic receipt again from the server via the output control apparatus.
Meanwhile, patent reference 2 discloses a technology for preventing double issuance of an electronic receipt. The patent reference 2 is designed to record, for each piece of sales data, whether an electronic receipt has already been issued for the piece of sales data. When an issuance request of an electronic receipt is received from a user, the technology prevents issuance of the electronic receipt if the electronic receipt has already been issued.
Patent Reference 1:
Japanese Laid-open patent application No. 2002-312853
Patent Reference 2:
Japanese Laid-open patent application No. 2003-203274